1. Field of the Invention
This invention relates to a metal-metal amorphous alloy for use in various magnetic heads and, more particularly, to a refractory amorphous alloy which has excellent thermal stability and excellent soft magnetic properties.
2. Description of the Prior Art
A metal-metal amorphous alloy has a higher crystallizing temperature, and more excellent corrosion resistance than a conventional metal-semimetal amorphous alloy containing nonmetal. And the amorphous alloy containing special components has smaller magnetostriction and excellent soft magnetic properties, and for this reason they have been used as the materials of magnetic heads which are treated through a thermal history, such as glass bonding.
Generally, conditions required for the amorphous alloy for use in magnetic heads are as described below.
(1) Magnetostriction (.lambda.s) is "0", or .lambda.s is nearly equal to "0". PA0 (2) Saturation magnetic flux density (Bs) is large. PA0 (3) Crystallization temperature (Tx) is high. PA0 (4) Heat resistance is high. PA0 (5) The relationship where Curie temperature (Tc) is lower than the crystallization temperature (Tx) is satisfied.
Of these conditions, with respect to the condition (1), the magnitude of the magnetostriction is very important. When an amorphous alloy thin film is formed on a ferrite substrate, for example, to manufacture a thin film magnetic head, magnetic anisotropy is induced in the amorphous alloy thin film by the stress generated according to the magnitude of the magnetostriction. Further, magnetic anisotropy is also induced by the thermal stress of glass bonding causing its thermal resistance to be deteriorated, and it is accordingly important to obtain a composition of .lambda.s=0 where s.perspectiveto.0. In order to obtain a magnetic head having high performance, it is needed to suppress the absolute value of the magnetostriction to approx. 5.times.10.sup.-7 or lower to a low magnetostriction.
Of the conditions, the condition (2) is entirely contradictory to the condition (5). More specifically, it is desired to provide large saturation magnetic flux density, but if the saturation magnetic flux density is increased, the crystallization temperature decreases, and the thermal resistance reduces. Further, when the saturation magnetic flux density is increased, the crystallization temperature (Tx) and the Curie temperature (Tc) are reversed so as not to hold the relationship of Tc smaller than Tx. Thus, there arises a drawback that a heat treatment above the Curie temperature becomes difficult for the purpose of eliminating magnetic anisotropy. In addition, in view of the mass productivity of the magnetic heads, when a heat treatment is conducted and the relationship of Tc less than Tx is not satisfied, it is necessary to anneal it in a magnetic field. Thus, a large scale facility for a magnetic field generator is required, and the quantity of the materials to be treated is limited to reduce its productivity.
Therefore, if the relationship of Tc less than Tx is satisfied in the amorphous alloy, a nonmagnetic field annealing can be realized, and an annealing can be performed simultaneously upon glass bonding.
Then, Co-Nb-Zn amorphous alloy is heretofore known as an alloy for satisfying these conditions, and the temperature for stably heat treating the alloy is known to range from 480.degree. C. to 500.degree. C.
When magnetic heads are manufactured through glass bonding, it is known to improve the reliability of the magnetic head by setting highly the treating temperature, but the glass bonding to be conducted at the treating temperature of approx. 480.degree. to 500.degree. C. like in the case of the above-mentioned Co-Nb-Zr amorphous alloy remarkably lacks the reliability at present, and drawbacks, such as corrosions feasibly occur, and the reliability of the magnetic head obtained through the glass bonding is accordingly insufficient. Recently, low melting point glass has been developed as a glass bonding material for use in the magnetic heads of the amorphous alloy and can be bonded at relatively low temperature, but the glass bonding using the low melting point glass has still less reliability.